The three general objectives of this project are: 1. Elucidation of the anemia of uremia in terms of the kinetics of red cell transport and metabolism, the effects of hemodialysis, and other extracellular influences. 2. Examination of the effects of mechanical stress on red cell structure and function. 3. Assessment of the interrelationship between anion and cation transport in red cells. The data which have been accumulated to date show that the permeability of red cells from uremic patients is not altered by a 4-6 hour hemodialysis procedure, and that red cell transport processes are not affected by this therapy. This applies to both twin-coil and sorbent systems. Subhemolytic shear stress forces increased permeability in both fresh and stored red cells. An anion carrier appears to be responsible for the increase in sodium influx in red cells exposed to high bicarbonate levels. Bumetanide, a new diuretic, decreases the permeability of the red cell membrane to sodium.